As per IS:2386 (Part IV)-1963, the aggregate crushing value shall NOT exceed _______ for concrete for wearing surfaces, such as runways, roads and pavements.
- A40%
- B20%
- C30%Correct
- D10%
Solution
Concept
Limit of aggregate crushing value for wearing surfaces is 30%. For other (non-wearing) concrete it is 45%.
Formula
Aggregate crushing value = (W2/W1) × 100
Step-by-step solution
1. Aggregate crushing value shows resistance of aggregate to crushing under gradual load. 2. For wearing surfaces (roads, runways, pavements), the limit is 30%. 3. For other concrete, the limit is 45%. 4. So the answer is 30%.
Explanation
Wearing surfaces face heavy traffic and abrasion, so they need strong aggregate. The crushing value must not be more than 30%. For non-wearing concrete, up to 45% is allowed.
Why the other options are wrong
A: 40% is not a standard limit (non-wearing limit is 45%). B: 20% is too strict and is not the code limit. D: 10% is far too strict and is not the code limit.
Shortcut
Wearing surface 30%, other concrete 45%.
Common mistake
Mixing up the 30% wearing-surface limit with the 45% limit for other concrete.
Correct answer: C) 30%